Octane Rating

[BRIAN_MP5T]

So why not everyone run 89... on the chance that half of us are correct

 

[CX-SV]

So why not everyone run 89... on the chance that half of us are correct

Same answer, waste of money (even if "mind tricks" are involved, see post #1).

 

[youzi]

Hey guys:

I swear there was a performance increase after the first tank of gas...either because of whatever gas that dealer put in at delivery (I swear by Chevron since my first car), or becasue of 91 octane, or becasue of car "breaking in". it felt different and I also did not feel the same performance and exhaust sound compared to the demo cs-5 that I drove before buying my own. I definetely felt something...

 

[CX-SV]

^ What was felt were "mind tricks" combined with auto tranny adapting to driver (the improved responsiveness of tranny is noticeable)..

I felt the weather was nice this afternoon, 79 degrees F.

 

[leedos]

I'm averaging 27.5 nearly all city using 91 octane since new. I just cracked 2700 miles on my car and I can say it feels well broken in at this point. My fuel economy has also stabilized. I just filled up with 87 octane from QT to see what would happen. Maybe it's just me, my driving, my climate, the brand of gas, or the fact that I have a manual transmission, but I did notice a decrease in performance. Engine oil may make a minor difference, so note that I changed my oil at 2000 miles using Mobil 1 0w-20.

That said I don't think doing a back to back 87 vs 91 octane comparison is vaild. The ECU adjusts fueling and ignition timing to your car and climate. This correction process takes at least two full warmup cycles with varied RPMS's and load. If you change fuel grades, your engine tuning will be "off". After burning about 1/4 tank of 87, the engine seems to have adjusted itself to the different gas and performance has come back some, but not all the way. I'll go run 1 or 2 more full tanks of 87 from Chevron to see if performance returns. The 91 octane only costs me an extra $2-$3 per fillup. For even for a minor perfomance increase, l consider it money well spent with the way I drive. I'm actually quite pleased with my fuel economy so saving money is not really the issue for me. I use WOT to get up to speed on a regular basis, I refuse to impede traffic in the slightest degree.

<a href="http://www.fuelly.com/driver/leedos/cx5" target="_blank"><img src="http://mefi.us/images/fuelly/sig-us/130474.png" width="500" height="63" alt="Fuelly" title="Share and compare MPG at Fuelly" border="0"/></a>

I ran 3 tanks of 87 (Costco, QT, and Chevron) to verify that I am indeed getting worse gas mileage using 87 vs. 91. I can truthfully say that running 87 octane I'm getting around 23.8 MPG City, the dash reads slightly higher at 25.6. The dash reading being higher than actual seems to be consistent with what others are seeing as well. I accelerate more aggresviely than the EPA does so getting less that the window sticker doesn't surprise me at all. It was the same way with my last car (2002 Audi A4 1.8t).

Looking at my last three tanks of 91, I was getting 27.3 MPG 100% city. Averaging my last three tanks of 87, I'm was getting 24.5MPG with about 50 miles of highway driving. I also noticed when running 87 that my low fuel light would come on around 285 miles, running 91 it would come on around 315.

All said and done, for me, in my car, in my hot climate, driving in stop and go city traffic, filling my car with 91 octane actually cost less per mile. I get 6.901 miles per dollar running 87. I get 7.28 miles per dollar running premium. I suspect that those of you that aren't seeing any difference have the following things going for you:

1. You rarely use more the 50% throttle. Probably because you don't want your auto tranny to downshift. You just deal with or the lethargic low RPM acceleration of this car doesn't bother you.

2. Your climate is giving your lower intake air temps than I have. This helps the car run more timing. My intake air temps are around 135 degrees in the Arizona summer.

I'm not here to argue with other forum users on this, only to share my experience. It won't hurt my feelings if you think I'm full of BS and I'm playing "mind tricks" on myself. Why should you change if you are perfectly happy running 87? If you are not happy with MPG and performance and maybe you also live in a hot climate and drive a lot in stop and go why not try something different and come to your own conclusions. I'd recommend that you consider running 91 octance to improve your mileage. From my experience I've found that low RPM (less the 2500) acceleration is better and MPG is better. This will be my final post in this thread.

 

[IHeartGroceries]

People buy mid grade?

I think we MIGHT sell about 200-300 bbls of midgrade, out of the 20,000 bbls disposal we see for a day's throughput.
For this reason, it will never go into any of my vehicles. The liklihood of getting "bad" gas when buying midgrade is far higher than when buying regular or super.

 

[CX-5um]

I ran 3 tanks of 87 (Costco, QT, and Chevron) to verify that I am indeed getting worse gas mileage using 87 vs. 91. I can truthfully say that running 87 octane I'm getting around 23.8 MPG City, the dash reads slightly higher at 25.6. The dash reading being higher than actual seems to be consistent with what others are seeing as well. I accelerate more aggresviely than the EPA does so getting less that the window sticker doesn't surprise me at all. It was the same way with my last car (2002 Audi A4 1.8t).

Looking at my last three tanks of 91, I was getting 27.3 MPG 100% city. Averaging my last three tanks of 87, I'm was getting 24.5MPG with about 50 miles of highway driving. I also noticed when running 87 that my low fuel light would come on around 285 miles, running 91 it would come on around 315.

All said and done, for me, in my car, in my hot climate, driving in stop and go city traffic, filling my car with 91 octane actually cost less per mile. I get 6.901 miles per dollar running 87. I get 7.28 miles per dollar running premium. I suspect that those of you that aren't seeing any difference have the following things going for you:

1. You rarely use more the 50% throttle. Probably because you don't want your auto tranny to downshift. You just deal with or the lethargic low RPM acceleration of this car doesn't bother you.

2. Your climate is giving your lower intake air temps than I have. This helps the car run more timing. My intake air temps are around 135 degrees in the Arizona summer.

I'm not here to argue with other forum users on this, only to share my experience. It won't hurt my feelings if you think I'm full of BS and I'm playing "mind tricks" on myself. Why should you change if you are perfectly happy running 87? If you are not happy with MPG and performance and maybe you also live in a hot climate and drive a lot in stop and go why not try something different and come to your own conclusions. I'd recommend that you consider running 91 octance to improve your mileage. From my experience I've found that low RPM (less the 2500) acceleration is better and MPG is better. This will be my final post in this thread.

More power to you Leedos should you realize MPG gains with 91 octane vs 87. In the CX-5 I'm getting 27-28 city with AC driving 20 miles each way from Glendale, AZ to Scottsdale, AZ using 87 octane QT gas. Same temps you've come accross. I'm suspecting the reason you're seeing noticeable gains is that you're driving a manual vs mine which is an automatic? If you check specs for various new cars from various makes, the city mpgs have slightly higher ratings in autos vs manuals. It could be possible in real world driving with the CX-5 (uhm)

 

[V8toilet]

I ran 3 tanks of 87 (Costco, QT, and Chevron) to verify that I am indeed getting worse gas mileage using 87 vs. 91. I can truthfully say that running 87 octane I'm getting around 23.8 MPG City, the dash reads slightly higher at 25.6. The dash reading being higher than actual seems to be consistent with what others are seeing as well. I accelerate more aggresviely than the EPA does so getting less that the window sticker doesn't surprise me at all. It was the same way with my last car (2002 Audi A4 1.8t).

Looking at my last three tanks of 91, I was getting 27.3 MPG 100% city. Averaging my last three tanks of 87, I'm was getting 24.5MPG with about 50 miles of highway driving. I also noticed when running 87 that my low fuel light would come on around 285 miles, running 91 it would come on around 315.

All said and done, for me, in my car, in my hot climate, driving in stop and go city traffic, filling my car with 91 octane actually cost less per mile. I get 6.901 miles per dollar running 87. I get 7.28 miles per dollar running premium. I suspect that those of you that aren't seeing any difference have the following things going for you:

1. You rarely use more the 50% throttle. Probably because you don't want your auto tranny to downshift. You just deal with or the lethargic low RPM acceleration of this car doesn't bother you.

2. Your climate is giving your lower intake air temps than I have. This helps the car run more timing. My intake air temps are around 135 degrees in the Arizona summer.

I'm not here to argue with other forum users on this, only to share my experience. It won't hurt my feelings if you think I'm full of BS and I'm playing "mind tricks" on myself. Why should you change if you are perfectly happy running 87? If you are not happy with MPG and performance and maybe you also live in a hot climate and drive a lot in stop and go why not try something different and come to your own conclusions. I'd recommend that you consider running 91 octance to improve your mileage. From my experience I've found that low RPM (less the 2500) acceleration is better and MPG is better. This will be my final post in this thread.

Sorry man but there are too many variables like temperature, traffic, speed, wind, number of shifts, and inconsistent driving conditions in general for that test to prove anything. I can get those kind of fluctuations and not change the octane of the fuel driving the same places. When the manufacturers engineers think there will be a benefit for higher octane than they might put "use 87 octane or higher" in the owners manual. With older engines with 100,000 miles or more there is sometimes a benefit to higher octane because as they build up more carbon in them they can become less octane tolerant. With a new engine though I think you won't see any benefit for the vast majority of these Skyactive engines.

 

[erhayes]

I agree with V8toilet. However; I one insists on trying to prove this then I suggest the following. Run 10 full tanks of one octane gas using 10 different stations and do a statical analysis and a SD. Repeat using a different octane of your choice and do a statistical anal including a SD. Then compare to two values. Ed

 

[GAXIBM]

I agree with V8toilet. However; I one insists on trying to prove this then I suggest the following. Run 10 full tanks of one octane gas using 10 different stations and do a statical analysis and a SD. Repeat using a different octane of your choice and do a statistical anal including a SD. Then compare to two values. Ed

Also be sure to keep the outside temperture and humidity the same...

 

[DougNuts]

People buy mid grade?

I think we MIGHT sell about 200-300 bbls of midgrade, out of the 20,000 bbls disposal we see for a day's throughput.
For this reason, it will never go into any of my vehicles. The liklihood of getting "bad" gas when buying midgrade is far higher than when buying regular or super.

That only matters if your station doesn't make it's mid-grade by blending regular and premium.

 

[CX-SV]

Sorry man but there are too many variables like temperature, traffic, speed, wind, number of shifts, and inconsistent driving conditions in general for that test to prove anything. I can get those kind of fluctuations and not change the octane of the fuel driving the same places. When the manufacturers engineers think there will be a benefit for higher octane than they might put "use 87 octane or higher" in the owners manual. .

Yes regarding fluctuations in MPG are normal on 87 octange, not to mention mind tricks with perceptions of "low RPM (less than 2500) acceleration is better". This indicates running at lower RPM (because of perceptions just mentioned) on the higher octane which is exactly how this engine achieves best MPG (lower rpms, larger throttle opening, Atkinson cycle mode).

And here's the evidence of fluctuations in MPG using 100% 87 octane Chevron regular gasoline. All these tank MPG's which I track in a spreadsheet are based on my typical commute usage and weekend driving. I removed the tanks that had 100 miles of freeway driving (trips out of the area).

25.8
28.5
26.0
26.0
26.3
25.4
26.1
26.8
26.4
25.0
25.7
26.1
25.9
26.3
26.2
26.4
25.3
27.1
24.5
25.6
24.4
25.2
27.3
24.0
25.7
26.4

 

[CX-SV]

That only matters if your station doesn't make it's mid-grade by blending regular and premium.

So the question is this: Is midgrade blended at the pump or is it blended by the tanker truck and held in separate tank?

 

[erhayes]

Tank averages for the data that cx-sv recorded was 25.94 mpg with one Standard Deviation of 0.92.

 

[DougNuts]

So the question is this: Is midgrade blended at the pump or is it blended by the tanker truck and held in separate tank?

From what I have read, most modern stations blend on-site and do not have a separate tank.

 

[CX-SV]

From what I have read, most modern stations blend on-site and do not have a separate tank.

That's what I read (in CA at least).

 

[V8toilet]

In Leedos defense if an engine were to require a higher octane to prevent knock or ping (different situations define them) than the engine would realize some increased MPG in the vehicle and have better torque output too.

 

[IHeartGroceries]

That only matters if your station doesn't make it's mid-grade by blending regular and premium.

This is actually a good point...
Most filling stations do not have a separate mid grade tank.
But my statement regarding throughput still stands. Even if you buy mom n pop, buy from a mom n pop who disposes alot of petrol from their filling station.

So the question is this: Is midgrade blended at the pump or is it blended by the tanker truck and held in separate tank?

Tanker drivers do absolutely nothing but carry the fuel. They have no hand in blending, QC, etc, thank God.
But, to answer your question, it IS blended at the wholesale distribution level as well. It is essentially splash blended into the tanker's compartment. X amount of Regular is dispensed, then X amount of Premium is dispensed to achieve the driver's preset.

I will tell you this: If you for whatever reason fill up with mid grade, I'd be certain to fill from a filling station who stores mid grade on-site. I don't know about other states, but Texas so loosely enforces the calibration of dispencer meters at filling stations...there's no telling what you're actually getting.

Here at the loading terminals, our meters are proved quarterly, with daily evaluations of meter throughput and asset management. So, there's no question what is leaving our facility as mid grade is definitely mid grade.

 

[CX-SV]

Thanks, good reasons to avoid midblend, (not that it's recommended by Mazda for our CX-5's).

 

[CX-SV]

Bumping this up, it's been nearly a month since anybody reported on using high octane in the North American spec 2.0L gasser.